The patent invention relates to a method of producing can bodies from individual, planar, cut blanks and to an apparatus for implementing the method. Generally, round can bodies having a longitudinal seam can be produced according to two methods. In the first, each can is produced from an individual cut blank. According to the second, each can is cut from an elongated tube produced from a long flat band.
If the can bodies are produced from individual cut blanks, these pieces are individually taken from a magazine and are sent at a high speed through a rounding machine such as that taught in German Patent Document ("Offenlegnngsschrift") 3,330,171 in which the planar cut blank is converted to a round preform. At the end of the bending process, the bent cut blank drops into a collecting tray where it is quickly decelerated to a temporary stop. The rounded cut blank is then accelerated out of the transfer region of the rounding machine in its own axial direction, i.e. at 90.degree. to the direction of movement of the planar cut blank into the rounding machine, and is transported, generally at a noticeably higher speed than the joining speed, out of the collecting tray into a guide rail enclosed by a guiding device and further into a joining station.
The mode of operation of the rounding machine is divided into two distinct operations, forming can bodies and removing them from the collecting tray. The machine alternates between the bending and removal operations, accelerating the blank in one direction, stopping the blank and then accelerating the blank in a second direction. This mode of operation with constant deceleration by hard impact and sudden acceleration creates a high noise level. Moreover, due to the constant change from the rounding process to removal of the cut blank from the collecting tray, the output quantity of the machine is limited.
The production of long tubes having a welded longitudinal seam which are subsequently separated into individual can bodies in a separating station is taught, for example, in German Patent Document ("Offenlegnngschrift") 2,947,445. For shaping, a band is drawn through an outer, closed shaping tool which converges in the form of a funnel from a wider intake opening to an outlet opening which has a diameter corresponding to the can diameter. Although the continuous shaping of a band actually has great advantages with respect to noise production and with respect to the end result, problems do arise in creating the forces required to pull the sheet metal through the forming apparatus and to act on the exterior of the sheet metal.
In this process, before shaping and seam formation, the band may be provided with scoring lines corresponding to the length of the cans, with the separation into individual can bodes occurring in a separation station such as that taught in U.S. Pat. No. 3,430,410.
The shaping of individual blanks in an outer, funnel-shaped tool is difficult. The force of the shaping tool easily warps the can bodies and thus makes precise guidance impossible. Additionally, it is difficult to pull the cut blanks whose length is short compared to the length of the outer shaping tool because of interference between the shaping tool and the pulling mechanism.